Inserter systems such as those applicable for use with the present invention, are typically used by organizations such as banks, insurance companies and utility companies for producing a large volume of specific mailings where the contents of each mail item are directed to a particular addressee. Also, other organizations, such as direct mailers, use inserts for producing a large volume of generic mailings where the contents of each mail item are substantially identical for each addressee. Examples of such inserter systems are the 8 series, 9 series, and APS™ inserter systems available from Pitney Bowes Inc. of Stamford Conn.
In many respects, the typical inserter system resembles a manufacturing assembly line. Sheets and other raw materials (other sheets, enclosures, and envelopes) enter the inserter system as inputs. Then, a plurality of different modules or workstations in the inserter system work cooperatively to process the sheets until a finished mail piece is produced. The exact configuration of each inserter system depends upon the needs of each particular customer or installation.
Typically, inserter systems prepare mail pieces by gathering collations of documents on a conveyor. The collations are then transported on the conveyor to an insertion station where they are automatically stuffed into envelopes. After being stuffed with the collations, the envelopes are removed from the insertion station for further processing. Such further processing may include automated closing and sealing the envelope flap, weighing the envelope, applying postage to the envelope, and finally sorting and stacking the envelopes.
Current mail processing machines are often required to process up to 18,000 pieces of mail an hour. Such a high processing speed may require envelopes in an output subsystem to have a velocity in a range of 80-85 inches per second (ips) for processing. Consecutive envelopes will nominally be separated by a 200 ms time interval for proper processing while traveling through the inserter output subsystem. At such a high rate of speed, system modules, such as those for sealing envelopes and putting postage on envelopes, have very little time in which to perform their functions. If adequate control of spacing between envelopes is not maintained, the modules may not have time to perform their functions, envelopes may overlap, and jams and other errors may occur. In particular, postage meters are time sensitive components of a mail processing system. Meters must print a clear postal indicia on the appropriate part of the envelope to meet postal regulations. The meter must also have the time necessary to perform the necessary bookkeeping and calculations to ensure the appropriate funds are being stored and printed.
A typical postage meter used with a conventional high speed mail processing system has a mechanical print head that imprints postage indicia on envelopes being processed. Such conventional postage metering technology is available on Pitney Bowes R150 and R156 mailing machines using model 6500 meters. The mechanical print head is typically comprised of a rotary drum that impresses an ink image on envelopes traveling underneath. Using mechanical print head technology, throughput speed for meters is limited by considerations such as the meter's ability to calculate postage and update postage meter registers, and the speed at which ink can be applied to the envelopes. In most cases, solutions using mechanical print head technology have been found adequate for providing the desired throughput of approximately five envelopes per second.
However, use of existing mechanical print technology with high speed mail processing machines presents some challenges. First, some older mailing machines were not designed to operate at such high speeds for prolonged periods of time. Accordingly, solutions that allow printing to occur at lower speeds may be desirable in terms of enhancing long term mailing machine reliability.
Another problem is that many existing mechanical print head machines are configured such that once an envelope is in the mailing machine, it is committed to be printed and translated to a downstream module, regardless of downstream conditions. As a result, if there is a paper jam downstream, the existing mailing machine component could cause even more collateral damage to envelopes within the mailing machine. At such high rates, jams and resultant damage may be more severe than at lower speeds. Accordingly, improved control and lowered printing speed, while maintaining high throughput rate in a mechanical print head mailing machine could provide additional advantages.
Controlling throughput through the metering portion of a mail producing system is also a significant concern when using non-mechanical print heads. Many current mailing machines use digital printing technology to print postal indicia on envelopes. One form of digital printing that is commonly used for postage metering is thermal inkjet technology. Thermal inkjet technology has been found to be an effective method for generating images at 300 dpi on material translating up to 50 inches per second (ips) and 200 dpi at 80 ips. Thus, while thermal inkjet technology is recognized as useful, it is difficult to apply to high speed mail production systems that operate on mail pieces that are typically traveling in the range of up to 100 ips in such systems.
As postage meters using digital print technology become more prevalent in the marketplace, it is important to find suitable substitutes for the mechanical print technology meters that have traditionally been used in high speed mail production systems. This need for substitution is particularly important as it is expected that postal regulations will require phasing out of older mechanical print technology meters, and replacement with more sophisticated meters. Ink jet digital print technology is now capable of printing a desired 200 dpi resolution on paper traveling at 80 ips., but has not yet been incorporated in the metering portions of high speed mail production systems.
It is known that many standard ink jet print heads must be stopped occasionally in order to perform maintenance routines. In particular, “drop-on-demand” style ink jet print heads are known to require periodic maintenance. Maintenance may include a “print head wipe” that occurs approximately every 500 prints, and has a duration of approximately 3 seconds. Maintenance also may include a “print head purge” that occurs after approximately every 3000 prints, and has a duration of approximately 14 seconds. For an inserter operating at 18,000 pieces per hour, the wipe and purge activities would occur every 100 seconds and ten minutes respectively. These maintenance activities result in reduced throughput performance. For example, an inserter that would otherwise operate at 18,000 piece per hour, would be reduced to 17,000 pieces per hour as a result of purge and wipe print head maintenance.
More expensive ink jet technology is available that does not require such frequent maintenance. For example, Scitex™ ink jet printers can run continuously, will no significant interruption. However, such continuous printers can be prohibitively expensive, and it is preferred that less expensive drop-on-demand ink jet print head technology can be used.
Some systems that have been available from Pitney Bowes for a number of years address some issues relating to using a slower speed meter with a higher speed mail production system. These systems utilize mechanical print head R150 and R156 mailing machines using 6500 model postage meters installed on an inserter system. The postage meters operate at a slower velocity than that of upstream and downstream modules in the system. When an envelope reaches the postage meter module, a routine is initiated within the postage meter. Once the envelope is committed within the postage meter unit, this routine is carried out without regard to conditions outside the postage meter. The routine decelerates the envelope to a printing velocity. Then, the mechanical print head of the postage meters imprints an indicia on the envelope. After the indicia is printed, the envelope is accelerated back to close to the system velocity, and the envelope is transported out of the meter.
Using the R150 or R156 mailing machines in this manner postage can be printed on envelopes at a lower print velocity. However, problems still occur for systems operating at higher velocities, such as 80 ips. At this higher speed, the time interval between consecutive envelopes is so short that the R150 and R156 machines cannot reset itself in time to print an indicia on a second envelope. To solve this problem, Pitney Bowes has offered a solution for number of years utilizing two mailing machines arranged serially in the envelope transport path. A diagram of this prior art system is depicted in FIG. 1.
In this serial mailing machine solution, envelopes are transported along transport path 100. When a first of a series envelopes reaches the first serial mechanical mailing machine 101, the first envelope is decelerated for a printing operation by postage meter 104. After printing is complete, the first envelope is carried away from the first serial machine 101 via transport 102 to the second serial mechanical mailing machine 103.
At the second mailing machine 103, the first envelope is typically decelerated to the print velocity. However, since an indicia has already been printed on the first envelope, no printing operation is performed by the second postage meter 105. The first envelope is then accelerated back to the system velocity and carried out of the serial postage printing arrangement.
The motion control of deceleration and acceleration at the second postage meter 105 without performing a print operation is done in order to maintain the displacements of consecutive envelopes in the system. Failure to subject subsequent envelopes to the same displacements may result in one envelope catching up to the other and causing a jam.
Following the first envelope, a second envelope arrives at the first mailing machine 101. The second envelope is subjected to the deceleration and acceleration motion profile. In a high speed system, however, the first postage meter 104 may not have had time to reset to print another indicia. Accordingly, the second envelope passes through the first mailing machine 101 without a printing operation. The second envelope is then passed via transport 102 to the second mailing machine 103 where it is again decelerated to the print velocity. This time, mailing machine 103 does perform a printing operation and an indicia is printed on the second envelope by postage meter 105. Mailing machine 103 then accelerates the envelope back to the system velocity, and the second envelope is carried away downstream.
In this manner, some of the shortcomings of conventional mailing machines are avoided by allowing the serial mailing machines 101 and 103 to alternately take turns printing indicia on every-other envelope. One disadvantage of this serial arrangement is that it remains very sensitive to gaps sizes between consecutive envelopes. Gaps between subsequent envelopes are shortened every time a lead envelope undergoes the printing motion profile. If an error occurs in the processing to make the gap size smaller than expected, envelopes can catch-up to one another, and a paper jam can result. Also, the R150 and R156 mailing machines are a bit too long to have time to carry out printing motion profile before the arrival of the next envelope, and to still have some margin for error in the arrival of a subsequent envelope. As a result, envelopes can be passed off between sets of nips that are not going at the same speed, creating potential for pulling or buckling. Accordingly, a solution with better space utilization and that is less sensitive to gap size variation is desirable.
Another problem with existing solution is that the conventional postage meters are inflexible in adjusting to conditions present in upstream or downstream meters. For example, if the downstream module is halted as a result of a jam, the postage meter will continue to operate on whatever envelope is within its control. This often results in an additional jam, and collateral damage, as the postage meter attempts to output the envelope to a stopped downstream module.